1. Field of the Invention
The present invention relates to high-sensitivity reflection measurement apparatuses, and more particularly, to the implementation of higher-sensitivity measurement with a simplified structure.
2. Prior Art
In absorbance measuring methods, which evaluate a sample by its absorption characteristic, light transmitted through the sample is detected. These methods are not suited, however, to an infrared absorption measurement of a thin film having, for example, a thickness equal to or smaller than the wavelength of infrared light. In recent years, a high-sensitivity reflection method has been known as an effective method for the absorption measurement of such thin films in infrared spectroscopic methods.
In the high-sensitivity reflection method, light is incident on a sample at a large incident angle, and light reflected from the sample is detected to determine the optical absorption state of the sample surface under measurement. High-sensitivity reflection measurement apparatuses employing this method have also been developed (disclosed, for example, in Japanese Unexamined Patent Application Publication No. Hei-7-120379).
Even in such high-sensitivity reflection measurement apparatuses, further improvement of measurement sensitivity has been demanded. Although higher sensitivity with a simple structure has been strongly demanded, there has been conventionally no appropriate technology to implement it.